A head-mounted wearable mobile device allows digital content to be imposed directly in the line of sight of the user on the inside of the ‘lenses’ of the device, which are transparent digital displays. This effect is provides an overlay in at least part of the user's view to an environment through the lenses. Example digital content includes images, videos, textual content, maps, or the like. In some examples, the digital content is augmented reality content. Head-mounted and other wearable mobile devices expand possibilities for multi-user collaboration in various realms including the sharing of content. However, facilities are needed that assist users in collaboratively constructing digital models.